1. Field of the Invention
The present invention relates generally to water treatment compositions and methods of preparation and use. More particularly, the invention relates to solid water treatment compositions comprising a halogen source and an amine compound, methods of preparing solid water treatment compositions and methods for controlling biofouling, disinfecting, cleaning and water systems.
2. Description of Related Art
A wide variety of water systems are used for hygienic, recreational, commercial and industrial purposes. Typical water systems include cooling towers, swimming pools, spas, decorative fountains, dehumidifiers, waste water treatment systems, air conditioning and refrigeration systems, boiler treatment, desalination, food processing, ground and surface water, industrial effluent, industrial process water, oil field and petroleum processing, paper and pulp processing, septic and sewage treatment, laundry cleaning and sanitation systems, sink sanitizer systems in bars and restaurants, hard surface disinfectant systems in food service areas, disinfectant/sanitizer systems in the brewing industry, disinfectant systems for fruit and vegetable wash, ponds, reservoirs, potable water and toilets. A common problem associated with most types of water systems is contamination of the water by inorganic and organic debris entering the system. Water systems also provide conditions ideal for the growth of many types of microorganisms. Formation of microorganism deposits is known as biofouling and can occur on almost any surface exposed to an aqueous environment. Biofouling causes energy loss from the system due to increased transfer resistance on the system surfaces.
Prior art approaches to controlling biofouling, disinfecting and cleaning water systems include the use of hypohalite such as hypochlorites and hypobromites in various forms and combinations. As used herein, hypohalite refers to any compound that yields hypohalous acid, (HOX) or hypohalite ion (OX species wherein X is halogen when dissolved in water). Generally, a hypohalite source is added to the water to react with and eliminate contaminants. A specific concentration of free available halogen must be established and maintained for effective biofouling control, disinfecting and cleaning.
Hypohalite species disinfect and clean water by reacting with debris and microorganisms that interfere with sanitary conditions in the water. The hypohalite species eliminate the contaminants by chemical oxidation that produces innocuous reaction products. Because there are many types of contaminants that can react with the hypohalite species, many possible reactions can occur and a multitude of by-reaction products are formed. The majority of contaminants, however, comprise various forms of naturally occurring nitrogen compounds. The nitrogen compounds are destroyed by the reaction of the compound with hypohalous acid. The reaction results in the formation of nitrogen, carbon dioxide, water, chlorides and water soluble organic substances. As a result, the water is cleaned and sanitized.
The concentration of the hypohalite species can be determined by several methods and is commonly expressed in terms of parts per million (ppm) of free available halogen, generally chlorine or bromine. The optimum free available halogen concentration varies in a water system depending on the type of system and other environmental factors that must be taken into consideration. Cooling tower water generally requires free and combined available chlorine from about 1.0 to 10 ppm; swimming pools generally require free available chlorine from about 1.0 to 5.0 ppm; spas generally require free available chlorine from about 3.0 to 5.0 ppm; toilet water generally requires free and combined available chlorine from about 2 to 30 ppm; potable water generally requires free and available chlorine from about 2.0 to 3.0 ppm; and cleaning and sanitizing solution generally requires chlorine from about 100 ppm. The amount of free available chlorine or bromine necessary for treating a particular system is well known in the art.
The most economical and widely used source of free available halogen is gaseous chlorine as evidenced by the fact that it is used to disinfect  greater than 99% of the public drinking water supplies and  greater than 95% of the municipal public swimming pools. Gaseous chlorine is inexpensive and has excellent disinfecting properties. The free chlorine residuals in the water are easy to maintain and monitor throughout the water distribution systems. However, the free chlorine residuals are unstable in bodies of water that are exposed directly to sunlight. The decomposition of the chlorine residuals is due the UV rays. The half-life of the chlorine residuals range from 2-4 hours depending upon the temperature of the water and the intensity of the sunlight. To maintain the optimum free chlorine residual in the water system, gaseous chlorine must be continually fed into the water system to replace the free chlorine lost to UV degradation and reactions involved in the disinfecting of the water. In addition, gaseous chlorine is hazardous and requires a high level of technical expertise to control the gaseous feed system and prevent the release of hazardous amounts to the environment. As a consequence, other halogen sources are preferred over gaseous chlorine in many of the water treatment applications, particularly, residential, small public and private club swimming pools and mid-size cooling water recirculation systems.
Various attempts have been made to develop hypohalite-generating products that overcome the problems associated with gaseous chlorine. One of the most successful product developments has been the compressed forms such as, tablets, pucks, sticks, and the like of trichloroisocyanuric acid (TCCA). TCCA is now widely used to disinfect residential, small public and private club swimming pools. TCCA has significant advantages over other products because it generates cyanuric acid which reduces the degradation of the free chlorine residuals by UV. Also, the free available chlorine content of TCCA is typically 90.5% which is considerably higher ( greater than 25%) than other products, except gaseous chlorine which is 100%. In addition, it is easily compressed into solid forms that permit its use in simple low-cost dissolving devices such as erosion feeders, floating feeders and skimmers to chlorinate the water continuously. Moreover, TCCA is safer to use than gaseous chlorine.
Despite TCCA""s advantages over other chlorine products, disadvantages remain in its use in some water treatment applications. For instance, TCCA dissolves relatively fast in water. As a result, the concentration of the hypochlorite species in the water systems tend to be high, making the water acidic and corrosive. Additionally, chloramines, which have objectionable odors, are generated. The combination of these properties has prevented TCCA from becoming widely used as a sanitizer in automatic toilet cleaning, spas and indoor swimming pool applications. TCCA can also form nitrogen trichloride, a very hazardous compound that detonates readily when subjected to small mechanical, electrical or thermal shocks. This disadvantage prevents TCCA from becoming widely used in many cooling water treatment applications.
Attempts have been made to develop hypobromite products as an alternative to TCCA and other hypochlorite products. The most successful ones have been bromochlorohydantoins such as 1-bromo, 3-chloro-5,5-dimethyhydantoin (BCDMH) and a composition comprising 60 weight percent 1-bromo-3-chloro-dimethyl hydantoin, 30 weight percent dichloro-dimethyl hydantoin and 10 weight percent 1,3-dichloro-5-ethyl, 5-methyl hydantoin (BCEMH). For example, the BCEMH may comprise 60 weight percent 1-bromo-3-chloro-dimethyl hydantoin, 27.4 weight percent dichloro-dimethyl hydantoin and 10.6 weight percent 1,3-dichloro-5-ethyl, 5-methyl hydantoin and 1 weigh percent sodium chloride. These products are now more widely used in indoor swimming pools, spas, automatic toilet bowl cleaning and mid-size cooling water treatment applications than chlorine products, because they overcome the objectionable chloramine odor associated with chlorine products and are more effective with current alkaline treatment practices for cooling water re-circulation systems. However, the products still are not widely used to disinfect outdoor swimming pools because the free bromine residuals (HOBr and OBr) are degraded very rapidly by UV rays and no suitable means has been devised to slow the degradation process significantly. Moreover, the cost of disinfecting water systems with bromine is at least two times as much as disinfecting with TCCA. In addition, a BCEMH type product has limited application in indoor swimming pools because it dissolves faster than the dominant bromine product, BCDMH.
Thus, TCCA could compete more successfully in the automatic toilet cleaner and water cooling treatment applications if a way is devised to control the dissolving rate of TCCA, reduce the acidity of the TCCA solutions, overcome the chloramine odor and resolve the nitrogen trichloride problem satisfactorily. In addition, BCEMH could compete more successfully with BCDMH if a way is devised to reduce the dissolving rate to a level similar to, or acceptably higher or lower than, that of BCDMH.
Thus, most water treatment compositions are limited in, or precluded from, use in some water treatment applications because of the inherent problems associated with the dissolving rate of the compositions. The halogen source is often the most expensive material used in the composition making the compositions relatively expensive to manufacture. Other attempts to control the optimum free available halogen have concentrated on preserving the hypohalite species after it has already been released into the solution. Thus, none of the prior art attempts have found satisfactory water treatment compositions with dissolving rates appropriate for a particular water system that are both convenient and cost effective to manufacture.
Thus, there is still a need in the art for a composition that can deliver a convenient cost effective water treatment composition with a controlled dissolving rate that is less corrosive to the water system without the undesirable halamine odor associated with compositions of the prior art. Preferably, the composition should be readily customized for a particular type of water system.
The solid water treatment composition of the invention comprises at least one halogen source and at least one amine compound. In one embodiment, the solid water treatment composition comprises a chlorine or bromine source or a combination thereof and at least one amine compound or combination thereof in a solid form wherein the at least one amine compound reduces the dissolving rate of the halogen source when water treatment composition is immersed in water or other aqueous solution, while maintaining the structural integrity of the solid form. The water treatment composition may further comprise a tabletting additive.
Another aspect of the invention is a method of preparing the water treatment composition. The method provides water treatment compositions wherein at least one halogen source and at least one amine compound react when the solid water treatment composition contacted with water or other aqueous solution.
To further achieve the object of the invention, the invention provides methods of using solid water treatment compositions of the invention for disinfecting, cleaning and controlling biofouling in water systems.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.